Electrochemical energy storage systems and methods featuring high open circuit potential

Abstract

The invention concerns flow batteries comprising: a first aqueous electrolyte comprising a first redox active material; a second aqueous electrolyte comprising a second redox active material; a first electrode in contact with the first aqueous electrolyte; a second electrode in contact with the second aqueous electrolyte and a separator disposed between the first aqueous electrolyte and the second aqueous electrolyte; the flow battery having an open circuit potential of at least 1.4 V, and is capable of operating or is operating at a current density at least about 50 mA/cm 2 , wherein both of the first and second redox active materials remain soluble in both the charged and discharged states. In certain embodiments, the redox active materials are metal ligand coordination compounds. The disclosure also describes systems comprising these flow batteries and methods of them.

What is claimed: 
     
       1. A flow battery comprising:
 a first aqueous electrolyte comprising a first redox active material; 
 a second aqueous electrolyte comprising a second redox active material; 
 a first electrode in contact with said first aqueous electrolyte in a first chamber containing said first aqueous electrolyte; 
 a second electrode in contact with said second aqueous electrolyte in a second chamber containing said second aqueous electrolyte; and 
 a separator disposed between said first aqueous electrolyte and said second aqueous electrolyte;
 wherein said first aqueous electrolyte and said second aqueous electrolyte are chosen such that said flow battery has an open circuit potential of at least 1.5 V, and said flow battery is capable of operating at a current density of at least 50 mA/cm 2 ; 
 wherein said first redox active material remains soluble in said first aqueous electrolyte in both a charged state and a discharged state thereof, and said second redox active material remains soluble in said second aqueous electrolyte in both a charged state and a discharged state thereof; and 
 wherein the flow battery contains only two electrolytes. 
 
 
     
     
       2. The flow battery of  claim 1 , wherein at least one of said first electrode and said second electrode is a carbon electrode. 
     
     
       3. The flow battery of  claim 1  or  claim 2 , wherein said first and second electrodes remain metal-free during operation of said flow battery. 
     
     
       4. The flow battery of  claim 1 , wherein at least one of said redox active materials is an organic compound substantially devoid of metal. 
     
     
       5. The flow battery of  claim 1 , wherein at least one of said first and second redox active materials comprises an aromatic compound. 
     
     
       6. The flow battery of  claim 1 , wherein at least one of said first and second redox active materials is a metal ligand coordination compound. 
     
     
       7. The flow battery of  claim 1  or  claim 6 , wherein said flow battery has an energy density of at least 30 watt hour/liter (Wh/L). 
     
     
       8. The flow battery of  claim 1  or  claim 6 , wherein at least one of said first aqueous electrolyte and said second aqueous electrolyte has a pH in a range of from about 1 to about 13. 
     
     
       9. The flow battery of  claim 1  or  claim 6 , wherein said first aqueous electrolyte, said second aqueous electrolyte, or both said first and second aqueous electrolytes has a pH in a range of from about 8 to about 13. 
     
     
       10. The flow battery of  claim 9 , wherein the pH is in a range of from about 10 to about 12. 
     
     
       11. The flow battery of  claim 10 , wherein the pH is in a range of from about 10.5 to about 11.5. 
     
     
       12. The flow battery of  claim 1  or  claim 6 , wherein the flow battery is capable of operating with a voltage efficiency of at least about 70%. 
     
     
       13. The flow battery of  claim 1  or  claim 6 , wherein said separator comprises an ionomer. 
     
     
       14. The flow battery of  claim 1  or  claim 6 , further comprising:
 a second electrolyte tank in fluidic communication with the second chamber and a first electrolyte tank in fluidic communication with the first chamber. 
 
     
     
       15. The flow battery of  claim 14 , further comprising:
 a pump capable of transporting a fluid between the second electrolyte tank and the second chamber, between the first electrolyte tank and the first chamber, or both. 
 
     
     
       16. A system comprising a flow battery of  claim 1  or  claim 6 , and further comprising:
 at least one electrolyte circulation loop in fluidic communication with said first chamber and said second chamber, said at least one electrolyte circulation loop comprising storage tanks and piping for containing and transporting the first and second aqueous electrolytes; 
 control hardware and software; and 
 a power conditioning unit. 
 
     
     
       17. The system of  claim 16 , wherein the system is connected to an electrical grid configured to provide renewables integration, peak load shifting, grid firming, baseload power generation/consumption, energy arbitrage, transmission and distribution asset deferral, weak grid support, frequency regulation, or a combination thereof. 
     
     
       18. The system of  claim 16 , wherein the system is configured to provide stable power for remote camps, forward operating bases, off-grid telecommunications, or remote sensors. 
     
     
       19. A method of operating a flow battery of  claim 1  or  claim 6 , said method comprising:
 charging said flow battery by an input of electrical energy or discharging said flow battery by a removal of electrical energy. 
 
     
     
       20. A method of operating a flow battery of  claim 1  or  claim 6 , said method comprising:
 applying a potential difference across the first and second electrodes, with an associated flow of electrons, so as to:
 reduce the first redox active material while oxidizing the second redox active material; or 
 oxidize the first redox active material while reducing the second redox active material. 
 
 
     
     
       21. A method of charging a flow battery of  claim 1  or  claim 6 , with an associated flow of electrons, said method comprising:
 applying a potential difference across the first and second electrodes, so as to:
 reduce the first redox active material; or 
 oxidize the second redox active material; or 
 both reduce the first redox active material and oxidize the second redox active material. 
 
 
     
     
       22. A method of discharging the flow battery of  claim 1  or  claim 6 , with an associated flow of electrons, said method comprising:
 applying a electrical load across the first and second electrodes, so as to:
 oxidize the first redox active material; or 
 reduce the second redox active material; or 
 both oxidize the first redox active material and reduce the second redox active material.